Mechanics

IS INTAKE MANIFOLD CAN AFFECT TIMING?

1989 Toyota Corolla • 100,000 miles

Idling is to rough. I tried to adjust timing but the timing is to far from 10deg almost 20deg I think. I tried to adjust idle mixture screw but it wont help. I changed sparkplug, cleaned the carburetor and distributor's contacts but the idling still moving up and down. Already checked vacuum cables.
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Pokalay
September 13, 2011.



These do have a habit of sucking in the inlet manifold, spray a little starter fluid around the manifold, if the revs pick up there is a leak, check this first.

Mhpautos
Sep 13, 2011.
Improper valve adjustment is another possible cause. So would a bad PCV valve and unequal engine compression pressure.

KHLow2008
Sep 13, 2011.
My engine is 5af shim type and no need to adjust valve clearance. I tried to replaced gasket on intake manifold hope this will end up my trouble. Thanks for the quick reply.

Tiny
Pokalay
Sep 15, 2011.
Shim type does not mean valve adjustment is not necessary.

KHLow2008
Sep 15, 2011.
Shims are adjustable, they do wear. Clearence should be.010 on intake and.008 on exhaust (cold engine). You simply put a new shim in.

But the intake gasket can leak and if large enough will cause significant loss of power.

Mmprince4000
Sep 15, 2011.
Idling is now good and the engine is fine but I cant set the timing
to 10deg. I plugged 2 vacuum from distributor advance diaphram. 15deg is the lowest degree I can set. I already changed and checked the timing belt and set all timing marks, set the pulley at 0" TDC at the compression stroke and rotor at the spark#1. My current timing is 15degree. How can I reach 10 degree? Is my distributor faulty or my engine need to be top overhauled? My engine is toyota 89 model 4af carb with egr system.

Tiny
Pokalay
Oct 5, 2011.